This invention relates generally to apparatus used for cutting vegetation, and more particularly relates to a lawnmower and trimming implement of the type in which flexible nonmetallic cutting elements are mounted for rotation about a nearly vertical axis within a mower housing.
The present invention relates to a lawn mower in which cutting of grass is achieved by contact between the grass and free lengths of flexible nonmetallic filament mounted for rotation about a plurality of nearly vertical axes. The invention is drawn to an improvement in a lawn mower of the type which is generally disclosed in an application filed the same date as the present application, and entitled "Dual Element Filament Mower", in the names of Robert C. Comer and Henry Tillotson, the referred-to application being assigned to the same assignee as the present application.
Dual element filament mowers of the type disclosed in the application filed on behalf of Tillotson and Comer have a number of advantages over the prior art. Among these are lower power consumption, more maneuverability, and economies of manufacture. However, the present invention provides improvements in the quality and evenness of cut of a mower of this type without sacrificing such advantages.
One area of possible improvement noted in dual element filament mowers is in the quality of cut in the central area of the mower, that is that area directly forward of the overlapping zones of the adjacent cutting elements. It appears that, under certain cutting conditions, the combined air-pumping effect of two counter-rotating elements which overlap in the same cutting plane is to tend to "blow down" grass directly ahead of the overlapping zone on a line equidistant from the centers of rotation of the two elements. Also, since the elements are not normally synchronized, some contact between the flexible filaments occurs in the overlapping zone. This tends to result in line "flutter" which creates some unevenness of cut centrally of the mower.
Furthermore, in many applications, it desirable to have a combined mower and trimmer in which no bagging or collection of cut grass particles occurs. In filament cutting element type mowers, suspension and evacuation of the housing of the mower is not readily achieved, since the trailing sail portion which is usually found in rigid bladed mowers is missing. While comparable air circulation may be generated by using an on-axis fan suspended above a rotating cutting element, this is not particularly practical or economical, and defeats certain advantages inherent in a nonmetallic flexible filament mower. Therefore it is desirable to have a filament mower design which disburses cut grass particles as evenly as possible consistent with high quality of cut, yet prevents the recirculation and build-up of cut grass particles under the housing which one might normally expect absent an air-pumping system. The present invention is an improvement in dual element type filament mowers which is directed at these areas of need.